Vehicles operating in an autonomous mode (e.g., driverless) can relieve occupants, especially the driver, from some driving-related responsibilities. When operating in an autonomous mode, the vehicle can navigate to various locations using onboard sensors, allowing the vehicle to travel with minimal human interaction or in some cases without any passengers.
Speed control (throttle and brake control) is a critical operation in autonomous driving. Autonomous vehicles are required to apply a throttle control or a brake control to maneuver the autonomous vehicles around or to avoid obstacles autonomously following a planned route. A planned route may include speeding up, slowing down, or maintaining a reference speed from a starting location to a target location. However, because vehicular speed control is a delay system, i.e., the mechanical features of an autonomous vehicle responds with a time delay, and there are external factors such as, frictional force, wind resistances, steepness of the road, and initial errors, it may be a challenge to command an autonomous vehicle to follow a target reference speed while minimizing a difference between a target speed and an actual speed of the autonomous vehicle, also referred to as an autonomous driving vehicle or ADV.